Correct some straggling Ferret/Cursor interactions

Summary:
See PHI1182. Ref T13266. The recent fixes didn't quite cover the case where you have a query, but order by something other than relevance, and page forward.

Refine the tests around building/selecting these columns and paging values a little bit to be more specific about what they care about.

Test Plan:
Executed queries, then went to "Next Page", for:

• query text, non-relevance order.
• query text, relevance order.
• no query text, non-relevance order.
• no query text, relevance order.

Also, made an API call similar to the one in PHI1182.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13266

Differential Revision: https://secure.phabricator.com/D20354